Phase change cooling device and control method

ABSTRACT

Provided are a phase change cooling device and a control method, whereby stable high-efficiency cooling performance can be obtained according to heat exchange performance. This phase change cooling device includes: a heat receiver which accommodates a coolant and receives heat from a heat generation body which is to be cooled; a heat radiator which radiates the heat of a coolant vapor of the coolant gasified by receiving heat by means of the heat receiver, and recirculates a liquefied liquid coolant to the heat receiver; a valve for controlling the flow rate of the liquid coolant; and a control means for controlling the opening degree of the valve, wherein the control means controls the opening degree of the valve on the basis of an exhaust temperature, which is the temperature after being discharged from the heat receiver, and the temperature in the vicinity of the heat radiator.

TECHNICAL FIELD

The present invention relates to a phase change cooling device and a control method, particularly, to a phase change cooling device and a control method for transporting heat and radiating heat by virtue of a cycle of gasifying and condensing a coolant.

BACKGROUND ART

As a cloud service develops in recent years, an amount of required information-processing is continuously increasing. In order to process huge data, a data center that enhances energy efficiency by concentrating servers and pieces of network equipment at one place has been operating in various places. However, as an amount of information-processing increases in a data center, an amount of power consumption also increases in the data center.

In the data center, pieces of electronic equipment such as a central processing unit (CPU) and a large scale integration (LSI) are accommodated. These pieces of electronic equipment generate heat, and thus an air conditioner is used for maintaining an appropriate temperature in the data center. However, as an amount of information-processing increases, such an air conditioner also requires huge power.

Therefore, in order to reduce an operating cost of the data center, cutting down power for the air conditioner is an urgent matter. As one attempt of cutting down power for the air conditioner, a method of directly transporting heat, to an outside, which is discharged from a rack being a housing for accommodating electronic equipment, without passing through an air conditioner, and radiating the heat into outside air has been developed. Using such a method enables cutting down air conditioning power of the data center.

As a method of transporting heat, to an outside, which is discharged from a rack for accommodating electronic equipment, a method of utilizing a phase changing phenomenon of a coolant is known other than a method of circulating externally supplied cold water by means of a pump. In this method, a vaporization phenomenon which occurs when a phase of a coolant changes from a liquid-phase to a vapor-phase, and a condensation phenomenon which occurs when a phase of a coolant changes from a vapor-phase to a liquid-phase, constantly happen and thus cause a coolant to circulate. Since the method of using this phase changing phenomenon utilizes latent heat of the coolant, the method has a characteristic that a large amount of heat is transported. Because of this, the method is expected to serve as a means for cutting down power for the air conditioner of the data center.

One example of a phase change cooling device using a coolant circulation cycle caused by such a phase changing phenomenon of a coolant is described in Patent Literature 1 (PTL1).

A cooling system according to PTL1 includes a vaporizer provided near a server. The vaporizer is provided with a cooling coil therein, and a liquid coolant that flows in the cooling coil turns into gas by being vaporized by hot air generated from the server, and taking vaporization heat away from surroundings. The vaporizer is provided with a temperature sensor for measuring a temperature of air being the hot air that is discharged from the server, alter being cooled down in the vaporizer. An inlet of the cooling coil is provided with an expansion valve for adjusting a supply flow rate of a coolant to be supplied to the cooling coil. Based on a temperature measured by the temperature sensor, an opening degree of the expansion valve is automatically adjusted.

The vaporizer is connected to a return piping and a supply piping, and the return piping and the supply piping are provided with a cooling tower and a heat exchanger via an opening and closing valve.

Accordingly, a flow of a coolant between the cooling tower and the heat exchanger is configured to be switched based on a temperature and humidity of outside air.

CITATION LIST Patent Literature

[PTL1] Japanese Patent Application Laid-Open No. 2009-193245

SUMMARY OF INVENTION Technical Problem

The cooling system according to PTL1 causes, when including bot of the cooling tower and the heat exchanger for radiating heat, capital expenditure (CAPEX) to increase, thereby arises an issue that actual employment thereof is limited.

An object of the present invention is to provide a phase change cooling device and a control method that can acquire stable high-efficiency cooling performance according to heat exchange performance.

Solution to Problem

In order to achieve the object, a phase change cooling device according to the present invention includes: a heat receiver for accommodating a coolant and receiving heat from a heat generation body to be cooled; a heat radiator for radiating heat of a coolant vapor of the coolant gasified by receiving heat in the heat receiver, and recirculating a liquefied liquid coolant to the heat receiver; a valve for controlling a flow rate of the liquid coolant; and a control means for controlling an opening degree of the valve, wherein the control means controls an opening degree of the valve by referring to an exhaust air temperature being a temperature of air after being discharged from the heat receiver, and a temperature in a vicinity of the heat radiator,

A control method according to the present invention, of a phase change cooling device which includes a heat receiver for accommodating a coolant and receiving heat from a heat generation body to be cooled, a heat radiator for radiating heat of a coolant vapor of the coolant gasified by receiving heat in the heat receiver, and recirculating a liquefied liquid coolant to the heat receiver, and a valve for controlling a flow rate of the liquid coolant, includes controlling an opening degree of the valve by referring to an exhaust air temperature being a temperature of air after being discharged from a heat receiver, and a temperature in a vicinity of the heat radiator.

Advantageous Effects of Invention

The present invention is able to achieve stable high-efficiency cooling performance according to heat exchange performance.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a configuration diagram of a phase change cooling device of an example embodiment according to a generic concept of the present invention.

FIG. 2 is a configuration diagram of a phase change cooling device according to a first example embodiment.

FIG. 3 is a configuration diagram of a control unit 800 in FIG. 2.

FIG. 4 is a flowchart for determining a valve opening degree according to the first example embodiment.

FIG. 5 is a flowchart for explaining a flow of step S120 in FIG. 4 in more detail.

FIG. 6A is a configuration diagram of a data table and illustrates one example of an initial table and a table after being generated with data.

FIG. 6B is the configuration diagram of the data table and illustrates one example of the initial table and the table after being generated with data.

FIG. 7 is a configuration diagram of a phase change cooling device according to a second example embodiment.

FIG. 8 is a configuration diagram of a phase change cooling device according to a third example embodiment.

FIG. 9 is a configuration diagram of a phase change cooling device according to a fourth example embodiment.

FIG. 10 is a configuration diagram of a phase change cooling device according to a fifth example embodiment.

EXAMPLE EMBODIMENT

Preferred example embodiments of the present invention will be described in detail with reference to the drawings.

Before describing particular preferred example embodiments, a phase change cooling device and a control method of an example embodiment according to a generic concept of the present invention will be described. FIG. 1 is a configuration diagram of the phase change cooling device of the example embodiment according to the generic concept of the present invention.

The phase change cooling device in FIG. 1 includes: a heat receiver 11 for accommodating a coolant and receiving heat from a heat generation body to be cooled; a heat radiator 12 for radiating heat of a coolant vapor of the coolant gasified by receiving heat in the heat receiver 11, and recirculating a liquefied liquid coolant to the heat receiver 11; a valve 13 for controlling a flow rate of the liquid coolant; and a control means 14 for controlling an opening degree of the valve 13. Further, in the phase change cooling device in FIG. 1, the control means 14 controls an opening degree of the valve 13 by referring to an exhaust air temperature that is a temperature of air after being discharged from the heat receiver 11, and a temperature in a vicinity of the heat radiator 12.

Heat-radiating performance of the heat radiator 12 in FIG. 1 changes depending on a temperature of environment in which the heat radiator 12 is placed. Therefore, cooling performance of the phase change cooling device in FIG. 1 varies for each temperature of the environment in which the heat radiator 12 is placed. In the phase change cooling device in FIG. 1, the control means 14 controls an opening degree of the valve 13 by referring to an exhaust air temperature that is a temperature of air after being discharged from the heat receiver 11, and a temperature in a vicinity of the heat radiator 12. This enables an opening degree of the valve 13 to be optimally controlled for each temperature of the environment in which the heat radiator 12 is placed, and a liquid coolant with an optimal flow rate to be supplied to the heat receiver 11, hence stable high-efficiency cooling performance can be achieved, Hereinafter, more particular example embodiments will be described.

First Example Embodiment

First, a phase change cooling device and a control method according to a first example embodiment of the present invention will be described.

<Configuration>

FIG. 2 is a configuration diagram of a phase change cooling device 1000A according to the first example embodiment of the present invention. FIG. 3 is a configuration diagram of a control unit 800 in FIG. 2. FIG. 4 is a flowchart for determining a valve opening degree according to the first example embodiment. FIG. 5 is a flowchart for describing a flow of step S120 in FIG. 4 in more detail. FIGS. 6A and 6B are configuration diagrams of data tables.

The phase change cooling device 1000A in FIG. 2 transports heat and radiates heat between a heat receiver 210 of a local cooler 200 and outdoor equipment 500 by virtue of a cycle of gasifying and condensing a coolant. A housing 900 of the phase change cooling device 1000A in FIG. 2 is disposed with a plurality of heat receivers 210 in which a coolant boils by receiving exhaust heat of electronic equipment mounted on a rack 100 or the like, and a pump 710 for circulating a coolant. The outdoor equipment 500 for cooling a vapor-phase coolant that is gasified by receiving heat is disposed outside the housing 900. The outdoor equipment 500 includes a heat exchanger 520 and a fan 510 for sending air to the heat exchanger 520. A steam pipe 410 connects the heat receiver 210 and the outdoor equipment 500, a first liquid pipe 420 connects the heat exchanger 520 of the outdoor equipment 500 and the pump 710, and a second liquid pipe 440 connects the pump 710 and the heat receiver 210. Each pipe is formed in such a way that a coolant passes therein. The second liquid pipe 440 is connected with a valve 220.

Further, according to the present example embodiment, a heat receiver exhaust air temperature sensor 320 is disposed on an opposite side to the rack 100 across the heat receiver 210. The heat receiver exhaust air temperature sensor 320 acquires information on a heat receiver exhaust air temperature Tr_o being a temperature of air after passing through the heat receiver 210. Furthermore, an outside air temperature sensor 530 is disposed in a periphery of the outdoor equipment 500. The outside air temperature sensor 530 acquires information on an outside air temperature To in a periphery of the outdoor equipment 500.

A control unit 800 controls an opening degree of the valve 220. According to the present example embodiment, the control unit 800 changes an opening degree of the valve 220 by using the information on the heat receiver exhaust air temperature Tr_o being a temperature of air after passing through the heat receiver 210 and the information on the outside air temperature To, and based on proportional-integral-differential control (PID control). Under the PID control, a detection temperature (heat receiver exhaust air temperature) is controlled in such a way as to be closer to a target temperature.

A configuration of the control unit 800 in FIG. 2 will be described in more detail with reference to FIG. 3. The control unit 800 includes a determination unit including a temperature acquisition unit 811, a central control unit 812, and a data table 813 as a storage unit, and an output unit including a valve control unit 821 for controlling a valve. The temperature acquisition unit 811 acquires data from the heat receiver exhaust air temperature sensor 320 and the outside air temperature sensor 530. The valve control unit 821 controls an opening degree of the valve 220.

One example of the data table 813 will be described with reference to FIGS. 6A and 6B.

An initial table in FIG. 6A holds data on a table indicating relationship between an outside air temperature To and a valve opening degree OR,mem, a preserved heat receiver exhaust air temperature Tr_o,mem, and a preserved target temperature Tsp,mem. In FIG. 6A, by way of example of a table indicating relationship between an outside air temperature To and a valve opening degree OR,mem, a case in which the outside air temperature To is associated with the valve opening degree OR,mem for every 5° C. is illustrated. In a table after being generated with data in FIG. 6A, it is assumed that, when the outside air temperature To is equal to or less than 0° C., the valve opening degree OR,mem is 80%, when the outside air temperature To is above 0° C. and equal to or less than 5° C., the valve opening degree OR,mem is 75%, and when the outside air temperature To is above 25° C., the valve opening degree OR,mem is 0%.

By way of example, in the table after being generated with data in FIG. 6A, it is assumed that the preserved heat receiver exhaust air temperature Tr_o,mem is 29° C., and the preserved target temperature Tsp,mem is 28° C. In this case, by setting the target temperature Tsp at 28° C. while the heat receiver exhaust air temperature Tr_o is 29° C., the valve opening degree OR is controlled in such a way that the heat receiver exhaust air temperature Tr_o becomes 28° C.

The larger a difference between an outside air temperature and a heat receiver exhaust air temperature is, the greater cooling performance of the phase change cooling device becomes, and the smaller a difference between an outside air temperature and a heat receiver exhaust air temperature is, the lesser cooling performance of the phase change cooling device becomes. According to the example embodiment of the present invention, by preparing a table indicating relationship between an outside air temperature To and a valve opening degree OR_mem, a valve opening degree OR is controlled in such a way that the greater the cooling performance becomes due to a low outside air temperature To, the larger the valve opening degree OR becomes, and the lesser the cooling performance becomes due to a high outside air temperature To, the smaller the valve opening degree OR becomes.

Another example of the data table 813 is illustrated in FIG. 6B. An initial table in FIG. 6B holds a table indicating relationship between the outside air temperature To and the valve opening degree OR,mem and the preserved heat receiver exhaust air temperature Tr_o,mem, and the preserved target temperature Tsp,mem. By way of example of a table indicating relationship between the outside air temperature To, and the valve opening degree OR_mem and the heat receiver exhaust air temperature Tr_o,mem, a case in which the outside air temperature To is associated with the valve opening degree OR_mem and the heat receiver exhaust air temperature Tr_o,mem for every 5° C. is illustrated. In a table after being generated with data in FIG. 6B, it is assumed that, when the outside air temperature To is equal to or less than 0° C., the valve opening degree OR_mem is 80% and the heat receiver exhaust air temperature Tr_o,mem is 27° C., when the outside air temperature To is above 0° C. and equal to or less than 5° C., the valve opening degree OR_mem is 75% and the heat receiver exhaust air temperature Tr_o,mem is 27.5° C., and when the outside air temperature To is above 25° C., the valve opening degree OR_mem is 0% and the heat receiver exhaust air temperature Tr_o,mem is 35° C. By way of example, it is assumed that, in the table after being generated with data in FIG. 6B, the preserved target temperature Tsp,mem is 28° C.

<Operation>

Hereinafter, an operation will be described.

FIG. 4 is an algorithm for automatically changing an opening degree of the valve 220, based on information on the heat receiver exhaust air temperature sensor 320 and the outside air temperature sensor 530. In FIG. 4, while the PID control is used for a control part, a control method is not limited thereto.

First, after an outside air temperature To is acquired in S104, it is determined whether there are data on a valve opening degree OR,mem for each outside air temperature To in the data table 813 (whether there are data other than 0 being an initial value) (S105). In other words, in S105, it is determined whether data on the valve opening degree OR,mem that are other than 0 being an initial value exist in the data table 813 for each outside air temperature To. The initial table in FIG. 6B illustrates a case in which there is no data on the valve opening degree OR,mem for each outside air temperature To. When there is no data on the valve opening degree OR,mem for each outside air temperature To (No in S105), heat receiver exhaust air temperature data Tr_o,mem written in the data table 813, such as the table after being generated with data in FIG. 6B, are acquired and a valve opening degree is changed to a specified valve opening degree OR,mem written in the table (S106). After waiting for a prescribed time (S107) and the time has lapsed, the operation returns to S104 and the outside air temperature To is acquired.

When there are heat receiver exhaust air temperature data Tr_o,mem for each outside air temperature To (YES in S105), a target temperature Tsp of a heat receiver exhaust air temperature Tr_o is set to a target temperature initial value Tsp,ini, time Time is set to 0, and the heat receiver exhaust air temperature data Tr_o,mem are set to a heat receiver exhaust air temperature initial value Tr_o,ini (S108). After that, the operation moves on to step S111. Herein, the target temperature initial value Tsp,ini is set high. This means, set the target temperature initial value Tsp,ini as a value that can be achieved by the phase change cooling device 1000A regardless of the outside air temperature To and an amount of heat generated by the electronic equipment. Cooling performance of the phase change cooling device 1000A varies depending on the outside air temperature To and the amount of heat generated by the electronic equipment. This is because a lower limit value that can be achieved by the heat receiver exhaust air temperature Tr_o is changed.

In step S120, it is determined whether an absolute value of a difference between the heat receiver exhaust air temperature Tr_o and the heat receiver exhaust air temperature data Tr_o,mem stored in the data table 813 are greater than a threshold value Tr_o,th (S122). When it is determined YES in S122, it is determined that cooling performance (the heat receiver exhaust air temperature Tr_o) of the heat receiver 210 is changed, therefore, the operation moves on to S123 in order to update the data table 813. Herein, the change in the cooling performance of the heat receiver 210 is considered as, for example, a case in which a valve opening degree becomes inappropriate due to an amount of heat generated by the rack 100 increasing, or the like. On the other hand, when it is NO in S122, it is determined that the performance has not changed from before, therefore, there is no need to update the data table 813 and the operation returns to step S104.

In step S111, it is determined whether to fix a valve opening degree. For example, when using a mechanical valve for the valve 220, there is a limit on the number of times for opening and closing the valve, and constantly changing a valve opening degree greatly increases a risk of malfunction. A reason for determining whether to fix the valve opening degree is because, when the opening degree can be fixed, the risk can be reduced. When it is determined to fix the valve opening degree (S111, YES), the operation waits for a prescribed time (S113). On the other hand, when it is determined not to fix the valve opening degree (S111, NO), the valve opening degree is changed (S112), and the operation moves on to step S113.

Herein, the determination of fixing the valve is made from a fact that a deviation of a value of a heat receiver exhaust air temperature being tracked back for a certain prescribed time is small, that the temperature is getting closer to a target temperature, or the like. With regard to changing a valve opening degree, an opening degree of the valve is changed in such a way that a difference e between the heat receiver exhaust air temperature and the target temperature decreases.

Specifically, the opening degree is changed by using the PID control or the like.

After waiting for the prescribed time in step S113, it is determined whether time Time is greater than TimePID being a certain prescribed time (S114). TimePID is a typical time taken until control of the phase change cooling device 1000A is converged. When it is determined that Time is greater than TimePID (S114, YES), the operation goes to step S120. When it is determined that Time is smaller than TimePID (S114, NO), it is considered that the control is not converged, and the operation returns to step S111. In step S120, it is determined whether to change the target temperature Tsp. A specific flow of changing the target temperature Tsp is described in FIG. 5.

As described in FIG. 5, in step S121, a heat receiver exhaust air temperature Tr_o is acquired. Next, it is determined whether an absolute value of a difference between the heat receiver exhaust air temperature Tr_o and the heat receiver exhaust air temperature Tr_o,mem stored in the data table 813 is greater than a threshold value Tr_o,th (S122). When it is determined YES in S122, the performance increases, therefore, the target temperature Tsp, the heat receiver exhaust air temperature and the valve opening degree OR are stored in the data table (S123). Next, a new target temperature Tsp is calculated in accordance with an equation of step S124, and time is set as Time=0, then the operation returns to S111 and controls again. When it is determined NO in S122, it is determined that the performance is converged under a present condition (present outside air temperature To and heat generation of electronic equipment) and the operation returns to step S104,

Advantageous Effect

Heat-radiating performance of the heat exchanger 520 in FIG. 2 changes depending on an outside air temperature at which the heat exchanger 520 is placed. Thus, cooling performance of the phase change cooling device 1000A in FIG. 2 varies for each temperature of environment in which the heat exchanger 520 is placed. In the phase change cooling device 1000A in FIG. 2, the control unit 800 controls an opening degree of the valve 220 by referring to an exhaust air temperature that is a temperature of air after being discharged from the heat receiver 210, and a temperature in a vicinity of the heat exchanger 520. This enables an opening degree of the valve 220 to be optimally controlled for each temperature of environment in which the heat exchanger 520 is placed, and a liquid coolant with optimal flow rate to be supplied to the heat receiver 210, hence stable high-efficiency cooling performance can be achieved.

Second Example Embodiment

Next, a phase change cooling device and a control method according to a second example embodiment of the present invention will be described. FIG. 7 is a configuration diagram of the phase change cooling device according to the second example embodiment. A configuration similar to that of the phase change cooling device 1000A according to the first example embodiment is attached with a reference numeral identical with that of the phase change cooling device 1000A, and detailed description thereof is omitted.

A phase change cooling device 1000B in FIG. 7 transports heat and radiates heat between a heat receiver 210 of a local cooler 200 and outdoor equipment 500 by virtue of a cycle of gasifying and condensing a coolant. The phase change cooling device 1000E in FIG. 7 has a configuration similar to that of the phase change cooling device 1000A according to the first example embodiment, with an addition of a rack intake air temperature sensor 300 and a rack exhaust air temperature sensor 310. The rack intake temperature sensor 300 is disposed on an opposite side to the heat receiver 210 across a rack 100, and acquires information on a rack intake air temperature Ta. The rack exhaust air temperature sensor 310 is disposed between the rack 100 and the heat receiver 210, and acquires information on a rack exhaust air temperature Tr_i.

A control unit 800B controls an opening degree of a valve 220. The control unit 800B according to the present example embodiment changes, based on PID control, an opening degree of the valve 220 by using information on a heat receiver exhaust air temperature Tr_o being a temperature of air after passing through the heat receiver 210, information on an outside air temperature To, information on the rack intake air temperature Ta, and information on the rack exhaust air temperature Tr_i.

Specifically, the control unit 800B defines performance η calculated by η=(Tr_i−Tr_o)/(Tr_i−Ta)*100. Even in such an environment that the rack intake air temperature Ta and the rack exhaust air temperature Tr_i change, an opening degree of the valve 220 is changed, based on the PID control, from the rack intake air temperature Ta, the rack exhaust air temperature Tr_i, the heat receiver exhaust air temperature Tr_o, and the outside air temperature To.

Similarly to the first example embodiment, the present example embodiment enables an opening degree of the valve 220 to be optimally controlled for each temperature of environment in which a heat exchanger 520 is placed, and a liquid coolant with optimal flow rate to be supplied to the heat receiver 210, hence stable high-efficiency cooling performance can be achieved. Further, according to the present example embodiment, an opening degree of the valve 220 is controlled by also using the information on the rack intake air temperature Ta and the information on the rack exhaust air temperature Tr_i, and thus more precise control can be achieved compared with the control according to the first example embodiment.

Third Example Embodiment

Next, a phase change cooling device and a control method according to a third example embodiment of the present invention will be described. FIG. 8 is a configuration diagram of the phase change cooling device according to the third example embodiment. A configuration similar to that of the phase change cooling device 1000B according to the second example embodiment is attached with a reference numeral identical with that of the phase change cooling device 1000B, and detailed description thereof is omitted.

A phase change cooling device 10000 in FIG. 8 transports heat and radiates beat between a heat receiver 210 of a local cooler 200 and outdoor equipment 500 by virtue of a cycle of gasifying and condensing a coolant. The phase change cooling device 10000 in FIG. 8 has a configuration similar to that of the phase change cooling device 10003 according to the second example embodiment, with an addition of a reserve tank 610. The reserve tank 610 is disposed in a middle of a first liquid pipe 420 that connects a heat exchanger 520 of the outdoor equipment 500 and a pump 710.

In the phase change cooling device 1000C according to the present example embodiment, similarly to the phase change cooling device 10003 according to the second example embodiment, more precise control can be achieved.

Further, according to the present example embodiment, by having a buffer function of the added reserve tank 610, performance of the pump 710 and an amount of a coolant to be filled into a system from a piping configuration or the like do not need to be accurately determined. In addition, it is easily manageable even when a coolant flow rate changes due to a valve opening degree or the like changing.

Fourth Example Embodiment

Next, a phase change cooling device and a control method according to a fourth example embodiment of the present invention will be described. FIG. 9 is a configuration diagram of the phase change cooling device according to the fourth example embodiment. A configuration similar to that of the phase change cooling device 10003 according to the second example embodiment is attached with a reference numeral identical with that of the phase change cooling device 10003, and detailed description thereof is omitted.

A phase change cooling device 1000D in FIG. 9 transports heat and radiates heat between a heat receiver 210 of a local cooler 200 and outdoor equipment 500 by virtue of a cycle of gasifying and condensing a coolant. The phase change cooling device 1000D in FIG. 9 includes, instead of the steam pipe 410 of the phase change cooling device 1000B according to the second example embodiment, a steam pipe 410A and a steam pipe 410B. Further, the phase change cooling device 1000D includes a bypass pipe 450 for connecting a connection point between the steam pipe 410A and the steam pipe 410B, and a first liquid pipe 420. In the bypass pipe 450, a liquid-phase coolant that is pushed out into the steam pipe 410A without being vaporized in the heat receiver 210 flows toward the first liquid pipe 420.

In the phase change cooling device 1000D according to the present example embodiment, similarly to the phase change cooling device 1000B according to the second example embodiment, more precise control can be achieved.

Further, according to the present example embodiment, the liquid-phase coolant that is pushed out into the steam pipe 410A without being vaporized in the heat receiver 210 can be caused to return to the first liquid pipe 420 through the bypass pipe 450, and a pressure loss in the steam pipe 410B toward the outdoor equipment 500 can be reduced.

Fifth Example Embodiment

Next, a phase change cooling device and a control method according to a fifth example embodiment of the present invention will be described. FIG. 10 is a configuration diagram of the phase change cooling device according to the fifth example embodiment. A configuration similar to that of the phase change cooling device 10003 according to the second example embodiment is attached with a reference numeral identical with that of the phase change cooling device 1000B, and detailed description thereof is omitted.

A phase change cooling device 1000E in FIG. 10 transports heat and radiates heat between a heat receiver 210 of a local cooler 200 and outdoor equipment 500 by virtue of a cycle of gasifying and condensing a coolant. The phase change cooling device 1000E in FIG. 10 has a configuration similar to that of the phase change cooling device 10009 according to the second example embodiment, with an addition of a reserve tank 610 similar to that of the third example embodiment. The reserve tank 610 is disposed in a middle of a liquid pipe that connects a heat exchanger 520 of the outdoor equipment 500 and a pump 710. In other words, a liquid pipe 420A connects the heat exchanger 520 of the outdoor equipment 500 and the reserve tank 610, and a third liquid pipe 430 connects the reserve tank 610 and the pump 710. Further, the phase change cooling device 1000E in FIG. 10 includes, instead of the steam pipe 410 of the phase change cooling device 1000B according to the second example embodiment, a steam pipe 410A and a steam pipe 410B. Further, the phase change cooling device 1000E includes a bypass pipe 450B for connecting a connection point between the steam pipe 410A and the steam pipe 4103, and the reserve tank 610. In the bypass pipe 450B, a liquid-phase coolant that is pushed out into the steam pipe 410A without being vaporized in the heat receiver 210 flows toward the reserve tank 610.

In the phase change cooling device 1000E according to the present example embodiment, similarly to the phase change cooling device 1000B according to the second example embodiment, more precise control can be achieved.

Further, similarly to the third example embodiment, by having a buffer function of the added reserve tank 610, performance of the pump 710 and an amount of a coolant to be filled into a system from a piping configuration or the like do not need to be accurately determined. In addition, it is easily manageable even when a coolant flow rate changes due to a valve opening degree or the like changing.

Further, according to the present example embodiment, the liquid-phase coolant that is pushed out into the steam pipe 410A without being vaporized in the heat receiver 210 can be caused to return to the reserve tank 610 through the bypass pipe 450B, and a pressure loss in the steam pipe 410B toward the outdoor equipment 500 can be reduced.

While the invention has been described with preferable example embodiments thereof, the invention is not limited to these embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the claims.

This application is based upon and claims the benefit of priority from Japanese patent application No. 2017-189337, filed on Sep. 29, 2017, the disclosure of which is incorporated herein in its entirety by reference.

REFERENCE SIGNS LIST

-   -   100 Rack     -   200 Local cooler     -   210 Heat receiver     -   220 Valve     -   300 Rack intake air temperature sensor     -   310 Rack exhaust air temperature sensor     -   320 Heat receiver exhaust air temperature sensor     -   410 Steam pipe     -   420 First liquid pipe     -   430 Third liquid pipe     -   440 Second liquid pipe     -   500 Outdoor equipment     -   510 Fan     -   520 Heat exchanger     -   530 Outside air temperature sensor     -   610 Reserve tank     -   710 Pump     -   800 Control unit 

1. A phase change cooling device, comprising: a heat receiver for accommodating a coolant and receiving heat from a heat generation body to be cooled; a heat radiator for radiating heat of a coolant vapor of the coolant gasified by receiving heat in the heat receiver, and recirculating a liquefied liquid coolant to the heat receiver; a valve for controlling a flow rate of the liquid coolant; and a control unit that controls an opening degree of the valve, wherein the control unit controls an opening degree of the valve by referring to an exhaust air temperature being a temperature of air after being discharged from the heat receiver, and a temperature in a vicinity of the heat radiator.
 2. The phase change cooling device according to claim 1, wherein the control unit controls an opening degree of the valve by further referring to temperatures of air sent through the heat generation body, which are an inflow-side temperature toward the heat generation body and an outflow-side temperature from the heat generation body.
 3. The phase change cooling device according to claim 1, wherein the control unit controls an opening degree of the valve by stepwise updating a target temperature of the exhaust air temperature of the heat receiver for each temperature in a vicinity of the heat radiator.
 4. The phase change cooling device according to claim 3, wherein the control unit performs PID control on an opening degree of the valve in such a way that the exhaust air temperature of the heat receiver becomes closer to the target temperature.
 5. The phase change cooling device according to claim 4, wherein the control unit stepwise increases an opening degree of the valve in such a way that a difference between the exhaust air temperature of the heat receiver and the target temperature becomes equal to or less than a threshold value.
 6. The phase change cooling device according to claim 4, wherein the control unit stepwise decreases an opening degree of the valve in such a way that a difference between the exhaust air temperature of the heat receiver and the target temperature becomes equal to or less than a threshold value.
 7. A control method of a phase change cooling device that includes a heat receiver for accommodating a coolant and receiving heat from a heat generation body to be cooled, a heat radiator for radiating heat of a coolant vapor of the coolant gasified by receiving heat in the heat receiver, and recirculating a liquefied liquid coolant to the heat receiver, and a valve for controlling a flow rate of the liquid coolant, the control method comprising: controlling an opening degree of the valve by referring to an exhaust air temperature being a temperature of air after being discharged from a heat receiver, and a temperature in a vicinity of the heat radiator. 